Carbonized polymer point decorated bismuthyl carbonate / pyrenyl metal organic framework Z-type heterojunction as well as preparation method and application thereof

Abstract

The invention provides a carbonized polymer point decorated bismuthyl carbonate / pyrenyl metal organic framework Z-type heterojunction as well as a preparation method and application thereof, and belongs to the technical field of environmental functional materials. According to the material, CPDs are loaded on Bi2O2CO3 micro-nano flowers to form a compound, and a bismuth atom is shared through an interface and anchored on a bismuth-pyrenyl metal organic framework (Bi-TBAPy) to construct a Z-type heterojunction. The preparation method comprises the following steps: preparing CPDs by a microwave-assisted carbonization method, loading CPDs on Bi2O2CO3 by a hydrothermal method, synthesizing Bi-TBAPy by a solvothermal method, and finally compounding to construct the ternary heterojunction. The material can efficiently cooperate with photocatalytic reduction of Cr (VI) and degradation of antibiotics under irradiation of a 5W LED, the removal rate exceeds 90% within 80 min, and the material has excellent visible light response and stability and is suitable for complex wastewater treatment.

Description

Technical Field

[0001] This invention belongs to the field of environmental functional materials technology, and particularly relates to a carbonized polymer dot-decorated bismuth oxycarbonate / pyrene-based metal-organic framework Z-type heterojunction, its preparation method, and its application. Background Technology

[0002] In recent years, excessive levels of heavy metal ions and organic drug residues have been frequently detected in industrial wastewater, posing serious threats to human health and even the natural ecological cycle. Traditional wastewater treatment technologies such as adsorption, membrane filtration, chemical precipitation, and biodegradation are hampered by high maintenance costs, a tendency to cause secondary pollution, and limitations in the synergistic treatment of inorganic and organic pollutants, making it difficult to achieve satisfactory results. Photocatalysis, utilizing only solar energy, can simultaneously reduce inorganic metal ions and effectively mineralize organic drugs, thus being considered a promising alternative in the field of water purification.

[0003] Bismuth oxycarbonate (Bi₂O₂CO₃), with its suitable band structure, unique Sillén-Aurivillius configuration, and excellent resistance to photocorrosion, is an ideal candidate material for photocatalytic removal of pollutants. Its crystal structure is determined by [Bi₂O₂]. 2+ and [CO3] 2- The layers are stacked along the c-axis, which significantly shortens the migration distance of charge carriers from the exciton-bound region to the material surface and induces a built-in electric field and asymmetric polarization effect, giving it an advantage in suppressing random carrier recombination. However, Bi₂O₂CO₃ has a wide band gap (3.1-3.5 eV), making it unable to utilize the majority of visible light in sunlight; and its conduction band potential is too positive, resulting in insufficient reduction driving force. Therefore, reasonable improvements to the original Bi₂O₂CO₃ are needed to enhance its practical application potential.

[0004] Constructing Z-type heterojunctions is an effective strategy to improve redox potential and promote carrier separation to optimize photocatalytic activity. Based on this, researchers have synthesized g-C3N4 / Bi2O2CO3 [Appl. Catal. B-Environ. 353 (2024) 124050], Bi2S3 / Bi2O2CO3 [Surf. Interfaces 36 (2023) 102612], red phosphorus / Bi2O2CO3 [J. Colloid Interface Sci. 609 (2022) 320-329], BiOIO3 / Bi2O2CO3 [Sep. Purif. Technol. 370 (2025) 133197], Mo2C / Bi2O2CO3 [Sep. Purif. Technol. 353 (2025) 128186], and Bi4O5I2 / Bi2O2CO3 [Langmuir]. 41(22)(2025)14421-14435], Bi2O2CO3 / Ti3C2T x [Chem.Eng.J.452(2023)139327] and CuBi2O4 / Bi2O2CO3[Appl.Catal.B-Environ.340(2024)123246] and other Bi2O2CO3-based Z-type heterojunction materials have achieved significant progress in photocatalytic performance. However, most of the reducing semiconductors reported in the literature are inorganic materials, which cannot avoid the following problems: (1) the problem of insufficient visible light response has not been fundamentally improved; (2) the lattice matching of the two inorganic semiconductors is poor and the interface connection is loose, which hinders the interphase transport of charge carriers; (3) the pore structure is underdeveloped, and the adsorption of pollutants is insufficient, resulting in low utilization of the active species interface.

[0005] When used as a reducing semiconductor, organic porous crystalline materials have significant advantages over traditional inorganic materials in terms of tunability of electronic structure, specific surface area and porosity, and lattice matching ability. Symmetric pyrene tetracarboxylic acid is an emerging luminescent material with a structure similar to porphyrin, exhibiting high reduction potential (-0.7 to -1.1 eV), good hydrophilicity, broad spectral response, and long carrier excited-state lifetime. These properties theoretically fit well with the standards for constructing high-performance Bi2O2CO3-based organic-inorganic composites. However, according to the literature [J. Photoch. Photobio. A 435(2023)114292], direct composite of hydrogen-bonded organic frameworks (HOFs) constructed with a typical symmetrical pyrene tetracarboxylic acid 1,3,6,8-tetra(terebenzoic acid)pyrene (H4TBAPy) with semiconductors offers limited improvement in photocatalytic activity and poor chemical stability. This reflects the weak interfacial interaction between HOFs and inorganic semiconductors, mainly consisting of van der Waals forces and hydrogen bonds, making it difficult for composite photocatalysts obtained in this way to meet the needs of practical applications. Therefore, designing efficient and stable Bi2O2CO3-based organic-inorganic heterojunction photocatalysts remains challenging. Summary of the Invention

[0006] To overcome the limitations of existing technologies, this invention proposes a carbonized polymer dot-decorated bismuth oxycarbonate / pyrene-based metal-organic framework Z-type heterojunction, its preparation method, and its applications. The method features a simple synthesis process, and the resulting ternary heterojunction material exhibits excellent photocatalytic pollutant removal activity under 5W LED illumination, demonstrating high practical value.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] One objective of this invention is to provide a Z-type heterojunction of bismuth oxycarbonate / pyrene-based metal-organic framework decorated with carbonized polymer dots, comprising carbonized polymer dots (CPDs), bismuth oxycarbonate (Bi2O2CO3) micro-nanoflowers, and bismuth-pyrene-based metal-organic framework (Bi-TBAPy); the carbonized polymer dots are loaded on the bismuth oxycarbonate micro-nanoflowers to form a composite, and the composite is anchored on the bismuth-pyrene-based metal-organic framework by sharing bismuth atoms at the interface;

[0009] Wherein, based on the total mass of the bismuth-pyrene-based metal-organic framework and the complex being 100 mg, the mass percentage of the bismuth-pyrene-based metal-organic framework is 5-30 mg.

[0010] This invention first utilizes a simple microwave-assisted solvothermal carbonization method to obtain charge transfer devices (CPDs), which are then loaded onto Bi₂O₂CO₃ micro-nanoflowers to obtain a composite material. This composite material is then anchored to Bi-TBAPy via interfacial bismuth atom sharing. The tight O→Bi-O bonds formed at the Bi₂O₂CO₃ and Bi-TBAPy interface provide atomic-level charge transfer channels, accelerating the directional accumulation and separation of charges. The introduction of CPDs enriches the reactive sites on Bi₂O₂CO₃ and expands the light absorption range, further enhancing the built-in electric field through the electron donor effect. Through a Z-type charge transfer mechanism, the ternary hybrid material can simultaneously utilize the relatively negative reduction potentials of Bi-TBAPy and CPDs to achieve effective heavy metal ion reduction and antibiotic mineralization.

[0011] Furthermore, the carbonized polymer dots are quantum dots with an average size of less than 10 nm.

[0012] Furthermore, the bismuth oxycarbonate micro-nanoflowers are micro-nanoflower structures formed by the self-assembly of layers, and the carbonized polymer dots are uniformly dotted on the surface of the bismuth oxycarbonate micro-nanoflower layers.

[0013] Furthermore, the bismuth-pyrene-based metal-organic framework is based on a symmetrical pyrene tetracarboxylic acid ligand and Bi... 3+ Rod-shaped crystals formed by coordination.

[0014] The second objective of this invention is to provide a method for preparing a Z-type heterojunction of bismuth oxycarbonate / pyrene-based metal-organic framework decorated with carbonized polymer dots, comprising the following steps:

[0015] Biomass-derived carbonized polymer dots were prepared by microwave-assisted solvothermal carbonization.

[0016] The carbonized polymer dots were loaded onto bismuth oxycarbonate micro-nanoflowers using a hydrothermal method to obtain a composite.

[0017] The composite was combined with a bismuth-pyrene-based metal-organic framework to construct a Z-type heterojunction, thus obtaining a carbonized polymer dot-decorated bismuth oxycarbonate / pyrene-based metal-organic framework Z-type heterojunction (CPDs@Bi2O2CO3 / Bi-TBAPy Z-type heterojunction photocatalyst).

[0018] Furthermore, the preparation method of the carbonized polymer dots includes the following steps: dissolving tea residue powder and ethylenediamine in deionized water, ultrasonically dispersing and stirring, then carbonizing by microwave solvent heating, and after the reaction is completed, placing the obtained filtrate in a dialysis bag, adding water for purification, vacuum evaporation and collecting the black solid powder carbonized polymer dots (CPDs).

[0019] The ratio of tea residue powder to ethylenediamine is 1.0 g : (0.5-2.5) mL.

[0020] The specific steps for ultrasonic dispersion and stirring are as follows: first, ultrasonically disperse for 10-120 minutes, and then continue stirring for 30-180 minutes;

[0021] The specific steps of the microwave solvent heating carbonization treatment are as follows: microwave solvent heating carbonization treatment at 140-200℃ and 200-800W for 30-240 minutes;

[0022] The specific purification steps are as follows: place the filtrate in a 200-3000 Da dialysis bag, add water, and purify for 12-72 hours.

[0023] Further, the preparation method of the composite includes the following steps: dissolving carbonized polymer dots, anhydrous Na2CO3 and C6H5BiO7 in deionized water, ultrasonically dispersing and stirring, then reacting at 120-180℃ for 16-28h, filtering and collecting the product, washing with deionized water and ethanol alternately and vacuum drying to obtain the composite (CPDs@Bi2O2CO3 nanoflowers);

[0024] The mass ratio of the carbonized polymer dots, anhydrous Na2CO3, and C6H5BiO7 is 15mg:0.23g:0.8g.

[0025] The specific steps for ultrasonic dispersion and stirring are as follows: first, ultrasonically disperse for 5-60 minutes, and then continue stirring for 15-90 minutes.

[0026] Furthermore, the preparation method of the bismuth-pyrene-based metal-organic framework includes the following steps: [The text abruptly ends here, so the translation stops.] 3+ The soluble salt and the symmetrical pyrene tetracarboxylic acid ligand were dissolved in a mixed solvent, rapidly dispersed by ultrasonication and stirred, and then crystallized at 120-160℃ for 48-96 h. The product was collected by filtration and washed with DMF, and then dried under vacuum.

[0027] Wherein, the Bi 3+ The molar ratio of the soluble salt to the symmetrical pyrene tetracarboxylic acid ligand is 1:1;

[0028] The symmetrical pyrene tetracarboxylic acid ligands include 1,3,6,8-tetracarboxylic acid pyrene (H4TCPy), 1,3,6,8-tetra(parabenzoic acid)pyrene (H4TBAPy), or 6,6',6”,6”'-(pyrene-1,3,6,8-tetramethyl)tetra(2-naphthoic acid) (H4TNAPy);

[0029] The mixed solvent is composed of N,N-dimethylformamide (DMF), 1,4-dioxane and deionized water in a volume ratio of (1-4):(1-4):2;

[0030] The Bi 3+ The volume ratio of the solvent to the mixed solvent is 1 mmol: (50-200) mL;

[0031] The specific steps for rapid ultrasonic dispersion and stirring are as follows: ultrasonic stirring for 2-6 hours.

[0032] Furthermore, the construction method of the Z-type heterostructure includes the following steps: dissolving a bismuth-pyrene metal-organic framework in N,N-dimethylformamide (DMF), then adding the composite, ultrasonically dispersing the resulting mixture, heating it in an oil bath, filtering and collecting the solid product, washing it with ethanol and deionized water, and then drying it under vacuum;

[0033] The bismuth-pyrene-based metal-organic framework needs to be activated before being dissolved in DMF. The specific steps are as follows: the bismuth-pyrene-based metal-organic framework is immersed in acetone, and the solvent is evaporated under vacuum after the immersion is completed. The immersion time is 24-96 hours, and the ratio of the amount of bismuth-pyrene-based metal-organic framework to acetone is 8 mg: (1-5) mL.

[0034] The ratio of the amount of bismuth-pyrene-based metal-organic framework to N,N-dimethylformamide is (5-30) mg: (50-100) mL;

[0035] Based on a total mass of 100 mg for the bismuth-pyrene-based metal-organic framework and the complex, the bismuth-pyrene-based metal-organic framework accounts for 5-30 mg.

[0036] The specific steps for the heat treatment are as follows: stir at 80-160℃ for 3-9 hours.

[0037] The third objective of this invention is to provide an application of a carbonized polymer dot-decorated bismuth oxycarbonate / pyrene-based metal-organic framework Z-type heterojunction in the photocatalytic synergistic removal of heavy metal ions and organic pollutants.

[0038] Compared with the prior art, the present invention has the following advantages and technical effects:

[0039] (1) Compared with traditional inorganic semiconductors, pyrene ligand materials have stronger visible light capture ability, more negative conduction band potential and longer carrier excited state lifetime, which makes the heterojunction have a great improvement in light absorption, reduction ability and carrier separation ability compared with the original Bi2O2CO3.

[0040] (2) Use the same Bi as Bi2O2CO3 3+ Constructing MOFs with pyrene ligands facilitates the interaction between the high density of oxygen atoms on the Bi2O2CO3 surface and the -COO atoms at the edges of the MOFs in the composite material. - Through the interface Bi 3+The O→Bi-O bonds formed by the reconstruction of surface bonds are connected. This strategy not only endows the material with atomic-level charge migration channels, promoting the directional accumulation and separation dynamics of charge carriers, but also effectively avoids the problem of poor material cycling stability caused by the weak interaction between hydrogen-bonded organic frameworks and inorganic semiconductors in previous technologies.

[0041] (3) CPDs are simple to synthesize, have a wide range of material sources, and contain abundant functional groups on their surface. Their introduction enriches the active sites on the surface of Bi2O2CO3 micro-nano flowers, and can further broaden the light absorption range by utilizing the upconversion luminescence properties. More importantly, the electron donor effect of CPDs can enhance the built-in electric field of the Bi2O2CO3 / Bi-TBAPy hetero interface and accelerate the directional accumulation of charge. Attached Figure Description

[0042] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0043] Figure 1 The chemical structures of H4TCPy, H4TBAPy, and H4TNAPy in the embodiments of the present invention are shown below;

[0044] Figure 2 This is a transmission electron microscope (TEM) image of the CPDs in Example 1;

[0045] Figure 3 The scanning electron microscope (SEM) of CPDs@Bi2O2CO3 in Example 1;

[0046] Figure 4 This is a TEM image of CPDs@Bi2O2CO3 in Example 1;

[0047] Figure 5 Here is a SEM image of Bi-TBAPy from Example 1;

[0048] Figure 6 The 1H and 1C NMR spectra of Bi-TBAPy in Example 1, and the possible coordination modes of MOFs obtained by analysis;

[0049] Figure 7 The image shows the SEM image of CPDs@Bi2O2CO3 / Bi-TBAPy obtained in Example 1.

[0050] Figure 8The UV-Vis diffuse reflectance (UV-Vis DRS) spectra of Bi2O2CO3 obtained in Comparative Example 1, CPDs, Bi-TBAPy, and CPDs@Bi2O2CO3 / Bi-TBAPy obtained in Example 1, and the Tauc curves with CPDs removed are shown.

[0051] Figure 9 The photocatalytic Cr(VI) removal performance curves are shown for Bi2O2CO3 obtained in Comparative Example 1, the binary Bi2O2CO3 / Bi-TBAPy obtained in Example 2, CPDs@Bi2O2CO3, Bi-TBAPy, and CPDs@Bi2O2CO3 / Bi-TBAPy obtained in Example 1.

[0052] Figure 10 The photocatalytic hexavalent chromium removal capacity of CPDs@Bi2O2CO3 / Bi-TBAPy ternary composites with different CPDs@Bi2O2CO3 to Bi-TBAPy mass ratios prepared in Examples 1-4;

[0053] Figure 11 The performance curves and rate constants of CPDs@Bi2O2CO3 / Bi-TBAPy prepared in Example 1 for synergistic and individual photocatalytic removal of Cr(VI) and levofloxacin are compared. Detailed Implementation

[0054] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0055] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0056] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0057] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0058] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0059] This invention provides a method for preparing a Z-type heterojunction of bismuth oxycarbonate / pyrene-based metal-organic framework decorated with carbonized polymer dots, comprising the following steps:

[0060] (1) Preparation of carbonized polymer dots (CPDs): Tea residue powder and ethylenediamine were mixed in a ratio of 1.0 g: (0.5-2.5) mL and dissolved in 10-30 mL of deionized water. The mixture was ultrasonically dispersed for 10-120 min and stirred for 30-180 min. Then, it was carbonized by microwave solvent heating at 140-200℃ and 200-800 W for 30-240 min. After the reaction, the filtrate was placed in a 200-3000 Da dialysis bag and purified with water for 12-72 h. The black solid powder CPDs were then collected by vacuum evaporation.

[0061] (2) Preparation of the composite (CPDs@Bi2O2CO3 nanoflowers): CPDs, anhydrous Na2CO3 and C6H5BiO7 were dissolved in deionized water, ultrasonically dispersed for 5-60 min and stirred for 15-90 min, and then reacted at 120-180℃ for 16-28 h. The product was collected by filtration, washed alternately with deionized water and ethanol and vacuum dried to obtain the composite.

[0062] (3) Preparation of Bi-TBAPy: Bi 3+ The soluble salt and the symmetrical pyrene tetracarboxylic acid ligand were dissolved in a mixed solvent, rapidly ultrasonically dispersed and stirred for 2-6 h, and then crystallized at 120-160 °C for 48-96 h. After the reaction was completed, the mixture was filtered and washed three times with DMF, and finally yellow rod-shaped crystals were collected and then vacuum dried to obtain Bi-TBAPy.

[0063] (4) Activation of Bi-TBAPy: Bi-TBAPy was immersed in acetone, and the solvent was evaporated under vacuum after the immersion was completed to obtain activated Bi-TBAPy;

[0064] (5) Construction of Z-type heterojunction: Dissolve 5-30 mg of activated Bi-TBAPy in 50-100 mL of N,N-dimethylformamide (DMF), and then add the composite to make the total amount of raw materials 100 mg. After ultrasonic dispersion for 15-90 min, the mixture is continuously magnetically stirred in an oil bath at 80-160 °C for 3-9 h. The solid product is collected by filtration, washed with ethanol and deionized water, and then dried under vacuum to obtain carbonized polymer dot-decorated bismuth oxycarbonate / pyrene metal-organic framework Z-type heterojunction (CPDs@Bi2O2CO3 / Bi-TBAPy Z-type heterojunction photocatalyst).

[0065] In some preferred embodiments of the present invention, in step (1), the tea residue powder is derived from Yunnan Menghai large-leaf Pu'er raw tea, the ratio of tea residue powder to ethylenediamine is 1.0g:1.5mL, the amount of deionized water used for dispersion is 20-25mL; the ultrasonic dispersion and stirring time are both 60min; the microwave heating temperature is 160℃, the power is 600W, and the time is 120min; a 2000Da dialysis bag is used for purification, and the purification time is 48h.

[0066] In some optional embodiments of the present invention, in step (2), the ratio of the amount of CPDs, anhydrous Na2CO3, C6H5BiO7 and deionized water is 15mg:0.23g:0.8g:(20-50)mL.

[0067] In some preferred embodiments of the present invention, in step (2), the amount of deionized water used is 35 mL; ultrasonic dispersion and stirring are performed for 30 min each; the hydrothermal temperature is 160 °C and the time is 24 h.

[0068] In some optional embodiments of the present invention, in step (3), the Bi 3+ The molar ratio of the symmetrical pyrene tetracarboxylic acid ligand is 1:1.

[0069] In some preferred embodiments of the present invention, in step (3), the Bi 3+ The soluble salt is stable and easily soluble Bi(NO3)3·5H2O.

[0070] In some optional embodiments of the present invention, in step (3), the symmetrical pyrene tetracarboxylic acid ligand includes 1,3,6,8-tetracarboxylic acid pyrene (H4TCPy, see [link]). Figure 1 a) 1,3,6,8-tetra(terebenzoic acid)pyrene (H4TBAPy, see [link]). Figure 1 (b) or 6,6',6”,6”'-(pyrene-1,3,6,8-tetramethyl)tetra(2-naphthoic acid) (H4TNAPy, see also) Figure 1(c) As an example, in some preferred embodiments of the invention, the ligand is a suitably sized H4TBAPy.

[0071] In some optional embodiments of the present invention, in step (3), the mixed solvent is composed of N,N-dimethylformamide, 1,4-dioxane, and deionized water, and the volume ratio of N,N-dimethylformamide, 1,4-dioxane, and deionized water is (1-4):(1-4):2. As an example, in some preferred embodiments of the present invention, the volume ratio of N,N-dimethylformamide, 1,4-dioxane, and deionized water is 2:1:2.

[0072] In some optional embodiments of the present invention, in step (3), the Bi 3+ The ratio of the soluble salt to the mixed solvent is 1 mmol:(50-200) mL. As an example, in some preferred embodiments of the present invention, the Bi... 3+ The ratio of the volume of the solvent to the volume of the mixed solvent is 1 mmol: 100 mL.

[0073] In some optional embodiments of the present invention, in step (3), the rapid ultrasonic dispersion and stirring are carried out for 3 hours, followed by crystallization at 130°C for 72 hours.

[0074] In some optional embodiments of the present invention, in step (4), the soaking time is 24-96 h, and the ratio of Bi-TBAPy to acetone is 8 mg:(1-5) mL. As an example, in some preferred embodiments of the present invention, the soaking time is 72 h, and the ratio of Bi-TBAPy to acetone is 8 mg:2 mL.

[0075] Using the above preparation method, a carbonized polymer dot-decorated bismuth oxycarbonate / pyrene metal-organic framework Z-type heterojunction (CPDs@Bi2O2CO3 / Bi-TBAPy Z-type heterojunction) can be prepared.

[0076] In some preferred embodiments of the present invention, in step (5), the amount of activated Bi-TBAPy is 15 mg, the volume of DMF is 80 mL, ultrasonic dispersion is performed for 60 min, the oil bath temperature is 120 °C, and the time is 6 h.

[0077] The carbonized polymer dot-decorated bismuth oxycarbonate / pyrene-based metal-organic framework Z-type heterojunction can be used in photocatalytic synergistic removal of heavy metal ions and organic pollutants.

[0078] The performance testing process of the CPDs@Bi2O2CO3 / Bi-TBAPy Z-type heterojunction prepared in this invention is as follows:

[0079] (1) Photocatalytic reduction of hexavalent chromium (Cr(VI)): 30 mg of catalyst sample and 50 mg / L K2Cr2O7 aqueous solution were added to a 50 mL high-transmittance photocatalytic reaction flask, followed by ultrasonic dispersion for 10 min. The treated suspension was transferred to the aforementioned multi-channel photocatalytic reaction system, and stirring was started at a rate of approximately 200 r / min. The dark reaction was continued for 60 min to ensure that the catalyst surface reached adsorption-desorption equilibrium. After the reaction was completed, stirring was maintained and a 5W LED light source (λ≥400 nm) was used. 3 mL of the reaction solution was taken as a sample at regular intervals. The samples were centrifuged to obtain the supernatant, and the concentration of Cr(VI) after color development was determined using the standard diphenylcarbazide method (GB 7467-87) at the maximum absorption wavelength of 540 nm.

[0080] (2) Photocatalytic synergistic removal of Cr(VI) and levofloxacin (LEV): In a 50 mL high-transmittance photocatalytic reaction flask, 30 mg of catalyst sample and a mixed solution of 20 mg / L LEV and 50 mg / L K2Cr2O7 were added, followed by ultrasonic dispersion for 10 min. The treated suspension was transferred to the aforementioned multi-channel photocatalytic reaction system, and stirring was started, with a stirring rate of approximately 200 r / min. The dark reaction was continued for 60 min to ensure that the catalyst surface reached adsorption-desorption equilibrium. After the reaction was completed, stirring was maintained and a 5W LED light source (λ≥400 nm) was used. 3 mL of the reaction solution was taken as a sample at regular intervals. The samples were centrifuged to obtain the supernatant. The concentration of Cr(VI) after color development was determined using the standard diphenylcarbazide method (GB 7467-87) at the maximum absorption wavelength of 540 nm, while the concentration of LEV was directly determined at its maximum absorption wavelength of 287 nm.

[0081] Unless otherwise specified, "room temperature" in this invention refers to 25±2℃.

[0082] Unless otherwise specified, all reagents, materials, and equipment used in the following embodiments of the present invention were commercially available. 1,3,6,8-Tetra(parabenzoic acid)pyrene (H4TBAPy) was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0083] The technical solution of the present invention will be further illustrated by the following embodiments.

[0084] Example 1

[0085] A method for preparing a Z-type heterojunction of bismuth oxycarbonate / pyrene-based metal-organic framework decorated with carbonized polymer dots, comprising the following steps:

[0086] (1) Dissolve 1.0g of Yunnan Menghai large-leaf Pu'er raw tea residue powder and 1.5mL of ethylenediamine in 20mL of deionized water, sonicate for 30min and stir vigorously for 60min; then transfer the resulting mixed solution to a 100mL polytetrafluoroethylene microwave reaction tube, react at 160℃ and 600W for 120min in a high-throughput closed microwave digestion workstation, cool to room temperature, and filter the mixture multiple times using a 0.22μm organic filter membrane to remove the filter residue; finally, place the obtained solution in a 2000Da regenerated cellulose dialysis bag, add deionized water and dialyze for 48h to obtain a clear yellow liquid, and after drying, obtain CPDs;

[0087] (2) Dissolve 15 mg of CPDs, 0.23 g of anhydrous Na2CO3 and 0.8 g of C6H5BiO7 in 35 mL of deionized water, sonicate for 30 min and then stir for 30 min. Then transfer to an 80 mL autoclave and react at 160 °C for 24 h. After the reaction is completed, cool to room temperature, filter and collect the white solid product, wash with deionized water and ethanol three times alternately, and finally vacuum dry at 60 °C for 8 h to obtain CPDs@Bi2O2CO3.

[0088] (3) 61.0 mg of Bi(NO3)·5H2O and 85.5 mg of H4TBAPy were dissolved in a mixed solvent (the mixed solvent was composed of DMF, Dioxane and deionized water in a volume ratio of 2:1:2) at a volume ratio of 12.5 mL, and ultrasonically dispersed and stirred vigorously for 3 h. The resulting mixed solution was then transferred to an 80 mL autoclave and kept at 130 °C for 72 h. After cooling to room temperature, it was filtered and washed three times with DMF. Finally, yellow rod-shaped Bi-TBAPy (about 40.0 mg, yield based on H4TBAPy of about 15.0%) was collected.

[0089] (4) 8 mg of Bi-TBAPy was soaked in 2 mL of acetone for 72 h. After the soaking, the solvent was evaporated under vacuum to obtain activated Bi-TBAPy.

[0090] (5) Take 15 mg of activated Bi-TBAPy and dissolve it in 80 mL of DMF. Then add 85 mg of CPDs@Bi2O2CO3 and sonicate for 60 min. Then, continuously stir magnetically in an oil bath at 120 °C for 6 h. After cooling to room temperature, filter and collect the solid sample. Wash thoroughly with ethanol and deionized water and then dry under vacuum to obtain a 15 wt.% CPDs@Bi2O2CO3 / Bi-TBAPy Z-type heterojunction sample.

[0091] Example 2

[0092] Same as Example 1, except that step (5) is as follows: 5 mg of activated Bi-TBAPy is dissolved in 80 mL of DMF, followed by 95 mg of CPDs@Bi2O2CO3, ultrasonically dispersed for 60 min, and then magnetically stirred continuously at 120 °C in an oil bath for 6 h. After cooling to room temperature, the solid sample is collected by filtration, thoroughly washed with ethanol and deionized water, and then dried under vacuum to obtain a 5 wt.% CPDs@Bi2O2CO3 / Bi-TBAPy Z-type heterojunction sample.

[0093] Example 3

[0094] Same as Example 1, except that step (5) is as follows: 10 mg of activated Bi-TBAPy is dissolved in 80 mL of DMF, followed by 90 mg of CPDs@Bi2O2CO3, ultrasonically dispersed for 60 min, and then magnetically stirred continuously at 120 °C in an oil bath for 6 h. After cooling to room temperature, the solid sample is collected by filtration, thoroughly washed with ethanol and deionized water, and then dried under vacuum to obtain a 10 wt.% CPDs@Bi2O2CO3 / Bi-TBAPy Z-type heterojunction sample.

[0095] Example 4

[0096] Same as Example 1, except that step (5) is as follows: 20 mg of activated Bi-TBAPy is dissolved in 80 mL of DMF, followed by 80 mg of CPDs@Bi2O2CO3, ultrasonically dispersed for 60 min, and then magnetically stirred continuously at 120 °C in an oil bath for 6 h. After cooling to room temperature, the solid sample is collected by filtration, thoroughly washed with ethanol and deionized water, and then dried under vacuum to obtain a 20 wt.% CPDs@Bi2O2CO3 / Bi-TBAPy Z-type heterojunction sample.

[0097] Comparative Example 1

[0098] A method for preparing a Bi2O2CO3 photocatalyst, comprising the following steps:

[0099] 0.23 g of anhydrous Na2CO3 and 0.8 g of C6H5BiO7 were dissolved in 35 mL of deionized water, ultrasonically dispersed for 30 min, and then stirred for 30 min. The mixture was then transferred to an 80 mL autoclave and reacted at 160 °C for 24 h. After the reaction was completed, the mixture was cooled to room temperature, filtered to collect the white solid product, and washed three times alternately with deionized water and ethanol. Finally, the product was vacuum dried at 60 °C for 8 h to obtain Bi2O2CO3.

[0100] Comparative Example 2

[0101] A method for preparing a binary bismuth oxycarbonate nanoflower / pyrene-based metal-organic framework Z-type heterostructure, using Bi-TBAPy from Example 1 and Bi2O2CO3 from Comparative Example 1 as raw materials, the specific steps are as follows:

[0102] (1) Dissolve 0.23 g of anhydrous Na2CO3 and 0.8 g of C6H5BiO7 in 35 mL of deionized water, sonicate for 30 min and then stir for 30 min. Then transfer to an 80 mL autoclave and react at 160 °C for 24 h. After the reaction is completed, cool to room temperature, filter and collect the white solid product, wash with deionized water and ethanol three times alternately, and finally vacuum dry at 60 °C for 8 h to obtain Bi2O2CO3.

[0103] (2) 61.0 mg of Bi(NO3)·5H2O and 85.5 mg of H4TBAPy were dissolved in a mixed solvent (the mixed solvent was composed of DMF, Dioxane and deionized water in a volume ratio of 2:1:2) at a volume ratio of 12.5 mL, and ultrasonically dispersed and stirred vigorously for 3 h. The resulting mixed solution was then transferred to an 80 mL autoclave and kept at 130 °C for 72 h. After cooling to room temperature, it was filtered and washed three times with DMF. Finally, yellow rod-shaped Bi-TBAPy was collected.

[0104] (3) 8 mg of Bi-TBAPy was soaked in 2 mL of acetone for 72 h. After the soaking, the solvent was evaporated under vacuum to obtain activated Bi-TBAPy.

[0105] (4) Dissolve 15 mg of the activated Bi-TBAPy obtained in step (3) in 80 mL of DMF, then add 85 mg of the Bi2O2CO3 photocatalyst prepared in step (1), ultrasonically disperse for 60 min, and then continuously magnetically stir in an oil bath at 120 °C for 6 h. After cooling to room temperature, filter and collect the solid sample, wash thoroughly with ethanol and deionized water, and then dry under vacuum to obtain the binary Bi2O2CO3 / Bi-TBAPy Z-type heterojunction.

[0106] 1. The CPDs prepared in step (1) of Example 1 were subjected to TEM detection, and the results are as follows: Figure 2 As shown, CPDs are quantum dot materials with an average size of less than 10 nm. Using them to modify Bi2O2CO3 can effectively enrich the reactive and adsorption active sites on the Bi2O2CO3 surface.

[0107] 2. The CPDs@Bi2O2CO3 prepared in step (2) of Example 1 were subjected to SEM and TEM detection, and the results are as follows: Figure 3 and Figure 4As shown, CPDs@Bi2O2CO3 consists of micro-nano flowers composed of Bi2O2CO3 sheets dotted with CPDs. This hierarchical structure can promote the utilization of light energy on the catalyst surface through the reflection and refraction of light, and is also beneficial for shortening the migration distance from the carrier confinement region to the interface layer.

[0108] 3. The Bi-TBAPy prepared in step (3) of Example 1 was subjected to SEM detection, and the results are as follows: Figure 5 As shown. This standard describes Bi-TBAPy as a regular rod-shaped crystal with a length of approximately 20 μm.

[0109] Further investigation using nuclear magnetic resonance (NMR) Figure 6 a and Figure 6 b) in the text confirms that Bi 3+ With TBAPy 4- The possible coordination modes of the linker are μ8-η. 1 η 1 η 1 η 1 η 1 η 1 η 1 η 1 andμ4-η 2 η 2 η 2 η 2 ( Figure 6 (c) in the middle.

[0110] 4. SEM analysis was performed on the CPDs@Bi2O2CO3 / Bi-TBAPy prepared in Example 1. The results are as follows: Figure 7 As shown in the figure, the CPDs@Bi2O2CO3 / Bi-TBAPy structure exhibits a capsule-like morphology formed by anchoring CPDs@Bi2O2CO3 with Bi-TBAPy microcrystals. Since photocatalytic reactions are primarily interfacial reactions, this encapsulation configuration can significantly reduce the amount of original Bi2O2CO3 required, which is beneficial for its practical application.

[0111] 5. Solid-state UV-Vis diffuse reflectance (SIR) tests were performed on four samples: Bi₂O₂CO₃ obtained in Comparative Example 1, CPDs obtained in Example 1, Bi-TBAPy, and CPDs@Bi₂O₂CO₃ / Bi-TBAPy. Figure 8 As shown in a), the results indicate that, relative to the original Bi₂O₂CO₃, the photoresponse band edge position of CPDs@Bi₂O₂CO₃ / Bi-TBAPy obtained in Example 1 significantly extends from 371 nm in the ultraviolet region to 513 nm in the visible region, and the band gap (2.18 eV) also significantly decreases (e.g., ...). Figure 8(b) This demonstrates that, with the excellent light-harvesting capabilities of both CPDs and Bi-TBAPy, Bi2O2CO3 significantly enhances the utilization of visible light, which dominates sunlight, greatly increasing its potential for practical applications.

[0112] 6. The photocatalytic hexavalent chromium removal capabilities of Bi2O2CO3 obtained in Comparative Example 1, the binary Bi2O2CO3 / Bi-TBAPy Z-type heterojunction obtained in Example 2, CPDs@Bi2O2CO3, Bi-TBAPy, and CPDs@Bi2O2CO3 / Bi-TBAPy obtained in Example 1 were evaluated. The uncatalyzed control group was used as a blank control. The results are as follows: Figure 9 As shown in the figure, the results indicate that CPDs@Bi2O2CO3 / Bi-TBAPy can achieve a removal rate of 91.2% for 50 mg / L hexavalent chromium within 80 min.

[0113] 7. The photocatalytic hexavalent chromium removal capacity of CPDs@Bi2O2CO3 / Bi-TBAPy ternary composites prepared from Examples 1-4 with different CPDs@Bi2O2CO3 to Bi-TBAPy mass ratios was evaluated. The results are as follows: Figure 10 As shown in the figure. The results indicate that the products obtained in Examples 1-4 achieved removal rates of 91.2%, 61.1%, 80.4%, and 51.2% for 50 mg / L hexavalent chromium within 80 min, respectively. It is evident that the ternary material containing 15 wt.% Bi-TBAPy prepared in Example 1 exhibits superior photocatalytic performance.

[0114] 8. The removal efficiency of CPDs@Bi2O2CO3 / Bi-TBAPy prepared in Example 1 on a single hexavalent chromium solution (50 mg / L), a single levofloxacin solution (20 mg / L), and a mixture of the two was evaluated. The results are as follows: Figure 11 As shown. From Figure 11 As can be seen, the removal rates of the ternary heterojunction all exceeded 90.0%. Furthermore, compared to single hexavalent chromium and levofloxacin solutions, the removal rates in the mixed system increased by 1.39 and 1.28 times, respectively. This indicates that the CPDs@Bi2O2CO3 / Bi-TBAPy obtained in Example 1 have excellent purification capabilities for both inorganic heavy metal ions and organic antibiotic wastewater.

[0115] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A Z-type heterojunction of bismuth oxycarbonate / pyrene-based metal-organic framework decorated with carbonized polymer dots, characterized in that, The invention comprises carbonized polymer dots, bismuth oxycarbonate micro-nanoflowers, and bismuth-pyrene-based metal-organic frameworks; the carbonized polymer dots are loaded on bismuth oxycarbonate micro-nanoflowers to form a complex, and the complex is anchored on the bismuth-pyrene-based metal-organic framework through the sharing of bismuth atoms at the interface.

2. The Z-type heterojunction of bismuth oxycarbonate / pyrene-based metal-organic framework decorated with carbonized polymer dots according to claim 1, characterized in that, The carbonized polymer dots are quantum dots with an average size of less than 10 nm.

3. The Z-type heterojunction of bismuth oxycarbonate / pyrene-based metal-organic framework decorated with carbonized polymer dots according to claim 1, characterized in that, The bismuth oxycarbonate micro-nanoflowers are micro-nanoflower structures formed by the self-assembly of layers, and the carbonized polymer dots are uniformly dotted on the surface of the bismuth oxycarbonate micro-nanoflower layers.

4. The Z-type heterojunction of bismuth oxycarbonate / pyrene-based metal-organic framework decorated with carbonized polymer dots according to claim 1, characterized in that, The bismuth-pyrene-based metal-organic framework is composed of a symmetrical pyrene tetracarboxylic acid ligand and Bi. 3+ Rod-shaped crystals formed by coordination.

5. A method for preparing a Z-type heterojunction of bismuth oxycarbonate / pyrene-based metal-organic framework decorated with carbonized polymer dots as described in any one of claims 1-4, characterized in that, Includes the following steps: Biomass-derived carbonized polymer dots were prepared by microwave-assisted solvothermal carbonization. The carbonized polymer dots were loaded onto bismuth oxycarbonate micro-nanoflowers using a hydrothermal method to obtain a composite. The composite was combined with a bismuth-pyrene-based metal-organic framework to construct a Z-shaped heterojunction, thus obtaining a bismuth oxycarbonate / pyrene-based metal-organic framework Z-shaped heterojunction decorated with carbonized polymer dots.

6. The preparation method according to claim 5, characterized in that, The preparation method of the carbonized polymer dots includes the following steps: dissolving tea residue powder and ethylenediamine in deionized water, ultrasonically dispersing and stirring, then carbonizing by microwave solvent heating, and after the reaction is completed, placing the obtained filtrate in a dialysis bag, adding water for purification, vacuum evaporation and collecting the black solid powder carbonized polymer dots. The ratio of tea residue powder to ethylenediamine is 1.0 g : (0.5-2.5) mL. The specific steps of the microwave solvent heating carbonization treatment are as follows: microwave solvent heating carbonization treatment at 140-200℃ and 200-800W for 30-240 minutes.

7. The preparation method according to claim 5, characterized in that, The preparation method of the composite includes the following steps: dissolving carbonized polymer dots, anhydrous Na2CO3 and C6H5BiO7 in deionized water, ultrasonically dispersing and stirring, then reacting at 120-180℃ for 16-28h, filtering and collecting the product, washing with deionized water and ethanol alternately and vacuum drying to obtain the composite. The mass ratio of the carbonized polymer dots, anhydrous Na2CO3, and C6H5BiO7 is 0.15:2.3:

8.

8. The preparation method according to claim 5, characterized in that, The preparation method of the bismuth-pyrene-based metal-organic framework includes the following steps: Bi 3+ The soluble salt and the symmetrical pyrene tetracarboxylic acid ligand were dissolved in a mixed solvent, rapidly dispersed by ultrasonication and stirred, and then crystallized at 120-160℃ for 48-96 h. The product was collected by filtration and washed with DMF, and then dried under vacuum. Wherein, the Bi 3+ The molar ratio of the soluble salt to the symmetrical pyrene tetracarboxylic acid ligand is 1:1; The symmetrical pyrene tetracarboxylic acid ligands include 1,3,6,8-tetracarboxylic acid pyrene, 1,3,6,8-tetra(parabenzoic acid)pyrene, or 6,6',6”,6”'-(pyrene-1,3,6,8-tetramethyl)tetra(2-naphthoic acid); The mixed solvent is composed of N,N-dimethylformamide, 1,4-dioxane and deionized water in a volume ratio of (1-4):(1-4):

2.

9. The preparation method according to claim 5, characterized in that, The method for constructing the Z-type heterostructure includes the following steps: dissolving a bismuth-pyrene metal-organic framework in N,N-dimethylformamide, then adding the composite, ultrasonically dispersing the resulting mixture, heating it in an oil bath, filtering and collecting the solid product, washing it with ethanol and deionized water, and then drying it under vacuum. The ratio of the amount of bismuth-pyrene-based metal-organic framework to N,N-dimethylformamide is (5-30) mg: (50-100) mL. Based on a total mass of 100 mg for the bismuth-pyrene-based metal-organic framework and the complex, the mass percentage of the bismuth-pyrene-based metal-organic framework is 5-30 mg. The specific steps for the heat treatment are as follows: stir at 80-160℃ for 3-9 hours.

10. The application of a carbonized polymer dot-decorated bismuth oxycarbonate / pyrene-based metal-organic framework Z-type heterojunction as described in any one of claims 1-4 in the photocatalytic synergistic removal of heavy metal ions and organic pollutants.

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